In recent years, with rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as a power source therefor has been emphasized. Further, also in the automobile industry and the like, the development of batteries having high output and high capacity for electric vehicles or hybrid vehicles has been advanced. Among various batteries, a lithium battery has been presently noticed from the viewpoint of a high energy density.
A liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and a structure for preventing a short circuit are necessary therefor. To the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery. Furthermore, a sulfide solid electrolyte material has been known as a solid electrolyte material used for such a solid electrolyte layer.
The sulfide solid electrolyte material has high Li ion conductivity and thus is useful for achieving high-output batteries. For this reason, various studies have been heretofore conducted on such a sulfide solid electrolyte material. For example, Patent Literature 1 discloses a composite material layer including sulfide glass uncalcined and an active material, in which the sulfide glass and the active material are pressure-formed and in contact with each other. Furthermore, Patent Literature 1 discloses that the sulfide glass is calcined at a temperature of the glass transition point or higher of the sulfide glass to have a portion of the sulfide glass transitioned to glass ceramic.